<!DOCTYPE html>
<html lang="en" dir="ltr" class="client-nojs">
<head>
<title>Parameter pack(since C++11) - cppreference.com</title>
<meta charset="UTF-8">
<meta name="generator" content="MediaWiki 1.21.2">
<link rel="shortcut icon" href="../../../common/favicon.ico">
<link rel="stylesheet" href="../../../common/ext.css">
<meta name="ResourceLoaderDynamicStyles" content="">
<link rel="stylesheet" href="../../../common/site_modules.css">
<style>a:lang(ar),a:lang(ckb),a:lang(fa),a:lang(kk-arab),a:lang(mzn),a:lang(ps),a:lang(ur){text-decoration:none}#toc{display:none}.editsection{display:none}
/* cache key: mwiki1-mwiki_en_:resourceloader:filter:minify-css:7:472787eddcf4605d11de8c7ef047234f */</style>

<script src="../../../common/startup_scripts.js"></script>
<script>if(window.mw){
mw.config.set({"wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"cpp/language/parameter_pack","wgTitle":"cpp/language/parameter pack","wgCurRevisionId":140905,"wgArticleId":9639,"wgIsArticle":true,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["Todo with reason"],"wgBreakFrames":false,"wgPageContentLanguage":"en","wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy","wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgMonthNamesShort":["","Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"],"wgRelevantPageName":"cpp/language/parameter_pack","wgRestrictionEdit":[],"wgRestrictionMove":[]});
}</script><script>if(window.mw){
mw.loader.implement("user.options",function(){mw.user.options.set({"ccmeonemails":0,"cols":80,"date":"default","diffonly":0,"disablemail":0,"disablesuggest":0,"editfont":"default","editondblclick":0,"editsection":0,"editsectiononrightclick":0,"enotifminoredits":0,"enotifrevealaddr":0,"enotifusertalkpages":1,"enotifwatchlistpages":0,"extendwatchlist":0,"externaldiff":0,"externaleditor":0,"fancysig":0,"forceeditsummary":0,"gender":"unknown","hideminor":0,"hidepatrolled":0,"imagesize":2,"justify":0,"math":1,"minordefault":0,"newpageshidepatrolled":0,"nocache":0,"noconvertlink":0,"norollbackdiff":0,"numberheadings":0,"previewonfirst":0,"previewontop":1,"quickbar":5,"rcdays":7,"rclimit":50,"rememberpassword":0,"rows":25,"searchlimit":20,"showhiddencats":0,"showjumplinks":1,"shownumberswatching":1,"showtoc":0,"showtoolbar":1,"skin":"cppreference2","stubthreshold":0,"thumbsize":2,"underline":2,"uselivepreview":0,"usenewrc":0,"watchcreations":0,"watchdefault":0,"watchdeletion":0,
"watchlistdays":3,"watchlisthideanons":0,"watchlisthidebots":0,"watchlisthideliu":0,"watchlisthideminor":0,"watchlisthideown":0,"watchlisthidepatrolled":0,"watchmoves":0,"wllimit":250,"variant":"en","language":"en","searchNs0":true,"searchNs1":false,"searchNs2":false,"searchNs3":false,"searchNs4":false,"searchNs5":false,"searchNs6":false,"searchNs7":false,"searchNs8":false,"searchNs9":false,"searchNs10":false,"searchNs11":false,"searchNs12":false,"searchNs13":false,"searchNs14":false,"searchNs15":false,"gadget-ColiruCompiler":1,"gadget-MathJax":1});;},{},{});mw.loader.implement("user.tokens",function(){mw.user.tokens.set({"editToken":"+\\","patrolToken":false,"watchToken":false});;},{},{});
/* cache key: mwiki1-mwiki_en_:resourceloader:filter:minify-js:7:9f05c6caceb9bb1a482b6cebd4c5a330 */
}</script>
<script>if(window.mw){
mw.loader.load(["mediawiki.page.startup","mediawiki.legacy.wikibits","mediawiki.legacy.ajax"]);
}</script>
<style type="text/css">/*<![CDATA[*/
.source-cpp {line-height: normal;}
.source-cpp li, .source-cpp pre {
	line-height: normal; border: 0px none white;
}
/**
 * GeSHi Dynamically Generated Stylesheet
 * --------------------------------------
 * Dynamically generated stylesheet for cpp
 * CSS class: source-cpp, CSS id: 
 * GeSHi (C) 2004 - 2007 Nigel McNie, 2007 - 2008 Benny Baumann
 * (http://qbnz.com/highlighter/ and http://geshi.org/)
 * --------------------------------------
 */
.cpp.source-cpp .de1, .cpp.source-cpp .de2 {font: normal normal 1em/1.2em monospace; margin:0; padding:0; background:none; vertical-align:top;}
.cpp.source-cpp  {font-family:monospace;}
.cpp.source-cpp .imp {font-weight: bold; color: red;}
.cpp.source-cpp li, .cpp.source-cpp .li1 {font-weight: normal; vertical-align:top;}
.cpp.source-cpp .ln {width:1px;text-align:right;margin:0;padding:0 2px;vertical-align:top;}
.cpp.source-cpp .li2 {font-weight: bold; vertical-align:top;}
.cpp.source-cpp .kw1 {color: #0000dd;}
.cpp.source-cpp .kw2 {color: #0000ff;}
.cpp.source-cpp .kw3 {color: #0000dd;}
.cpp.source-cpp .kw4 {color: #0000ff;}
.cpp.source-cpp .co1 {color: #909090;}
.cpp.source-cpp .co2 {color: #339900;}
.cpp.source-cpp .coMULTI {color: #ff0000; font-style: italic;}
.cpp.source-cpp .es0 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es1 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es2 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es3 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es4 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es5 {color: #008000; font-weight: bold;}
.cpp.source-cpp .br0 {color: #008000;}
.cpp.source-cpp .sy0 {color: #008000;}
.cpp.source-cpp .sy1 {color: #000080;}
.cpp.source-cpp .sy2 {color: #000040;}
.cpp.source-cpp .sy3 {color: #000040;}
.cpp.source-cpp .sy4 {color: #008080;}
.cpp.source-cpp .st0 {color: #008000;}
.cpp.source-cpp .nu0 {color: #000080;}
.cpp.source-cpp .nu6 {color: #000080;}
.cpp.source-cpp .nu8 {color: #000080;}
.cpp.source-cpp .nu12 {color: #000080;}
.cpp.source-cpp .nu16 {color:#000080;}
.cpp.source-cpp .nu17 {color:#000080;}
.cpp.source-cpp .nu18 {color:#000080;}
.cpp.source-cpp .nu19 {color:#000080;}
.cpp.source-cpp .ln-xtra, .cpp.source-cpp li.ln-xtra, .cpp.source-cpp div.ln-xtra {background-color: #ffc;}
.cpp.source-cpp span.xtra { display:block; }

/*]]>*/
</style><style type="text/css">/*<![CDATA[*/
.source-text {line-height: normal;}
.source-text li, .source-text pre {
	line-height: normal; border: 0px none white;
}
/**
 * GeSHi Dynamically Generated Stylesheet
 * --------------------------------------
 * Dynamically generated stylesheet for text
 * CSS class: source-text, CSS id: 
 * GeSHi (C) 2004 - 2007 Nigel McNie, 2007 - 2008 Benny Baumann
 * (http://qbnz.com/highlighter/ and http://geshi.org/)
 * --------------------------------------
 */
.text.source-text .de1, .text.source-text .de2 {font: normal normal 1em/1.2em monospace; margin:0; padding:0; background:none; vertical-align:top;}
.text.source-text  {font-family:monospace;}
.text.source-text .imp {font-weight: bold; color: red;}
.text.source-text li, .text.source-text .li1 {font-weight: normal; vertical-align:top;}
.text.source-text .ln {width:1px;text-align:right;margin:0;padding:0 2px;vertical-align:top;}
.text.source-text .li2 {font-weight: bold; vertical-align:top;}
.text.source-text .ln-xtra, .text.source-text li.ln-xtra, .text.source-text div.ln-xtra {background-color: #ffc;}
.text.source-text span.xtra { display:block; }

/*]]>*/
</style><!--[if lt IE 7]><style type="text/css">body{behavior:url("/mwiki/skins/cppreference2/csshover.min.htc")}</style><![endif]--></head>
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_language_parameter_pack skin-cppreference2 action-view cpp-navbar">
        <!-- header -->
        <!-- /header -->
        <!-- content -->
<div id="cpp-content-base">
            <div id="content">
                <a id="top"></a>
                <div id="mw-js-message" style="display:none;"></div>
                                <!-- firstHeading -->
<h1 id="firstHeading" class="firstHeading">Parameter pack<span class="t-mark-rev t-since-cxx11">(since C++11)</span></h1>
                <!-- /firstHeading -->
                <!-- bodyContent -->
                <div id="bodyContent">
                                        <!-- tagline -->
                    <div id="siteSub">From cppreference.com</div>
                    <!-- /tagline -->
                                        <!-- subtitle -->
                    <div id="contentSub"><span class="subpages">&lt; <a href="../../cpp.html" title="cpp">cpp</a>‎ | <a href="../language.html" title="cpp/language">language</a></span></div>
                    <!-- /subtitle -->
                                                            <!-- bodycontent -->
                    <div id="mw-content-text" lang="en" dir="ltr" class="mw-content-ltr"><div class="t-navbar" style=""><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../../cpp.html" title="cpp"> C++</a><div class="t-navbar-menu"><div><div><table class="t-nv-begin" cellpadding="0" style="line-height:1.1em;">
<tr class="t-nv"><td colspan="5"> <a href="../compiler_support.html" title="cpp/compiler support"> Compiler support</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../freestanding.html" title="cpp/freestanding"> Freestanding and hosted</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../language.html" title="cpp/language"> Language</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../header.html" title="cpp/header"> Standard library headers</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../named_req.html" title="cpp/named req"> Named requirements </a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../feature_test.html" title="cpp/feature test"> Feature test macros </a> <span class="t-mark-rev t-since-cxx20">(C++20)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../utility.html#Language_support" title="cpp/utility"> Language support library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../concepts.html" title="cpp/concepts"> Concepts library</a> <span class="t-mark-rev t-since-cxx20">(C++20)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../meta.html" title="cpp/meta"> Metaprogramming library</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../error.html" title="cpp/error"> Diagnostics library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../utility.html" title="cpp/utility"> General utilities library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../string.html" title="cpp/string"> Strings library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../container.html" title="cpp/container"> Containers library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../iterator.html" title="cpp/iterator"> Iterators library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../ranges.html" title="cpp/ranges"> Ranges library</a> <span class="t-mark-rev t-since-cxx20">(C++20)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../algorithm.html" title="cpp/algorithm"> Algorithms library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../numeric.html" title="cpp/numeric"> Numerics library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../locale.html" title="cpp/locale"> Localizations library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../io.html" title="cpp/io"> Input/output library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../filesystem.html" title="cpp/filesystem"> Filesystem library</a> <span class="t-mark-rev t-since-cxx17">(C++17)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../regex.html" title="cpp/regex"> Regular expressions library</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../thread.html" title="cpp/thread"> Concurrency support library</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../experimental.html" title="cpp/experimental"> Technical specifications</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../symbol_index.html" title="cpp/symbol index"> Symbols index</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../links/libs.html" title="cpp/links/libs"> External libraries</a> </td></tr>
</table></div><div></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../language.html" title="cpp/language"> C++ language</a><div class="t-navbar-menu"><div><div style="display:inline-block">
<div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv-h1"><td colspan="5"> General topics</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="../preprocessor.html" title="cpp/preprocessor"> Preprocessor</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../comments.html" title="cpp/comment"> Comments</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="../keywords.html" title="cpp/keyword"> Keywords</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="escape.html" title="cpp/language/escape"> Escape sequences</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> <a href="statements.html" title="cpp/language/statements"> Flow control</a></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Conditional execution statements</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="if.html" title="cpp/language/if"><tt>if</tt></a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="switch.html" title="cpp/language/switch"><tt>switch</tt></a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Iteration statements (loops)</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="for.html" title="cpp/language/for"><tt>for</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="range-for.html" title="cpp/language/range-for"> range-<code>for</code></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="while.html" title="cpp/language/while"><tt>while</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="do.html" title="cpp/language/do"> <code>do-while</code></a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Jump statements </td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="continue.html" title="cpp/language/continue"><tt>continue</tt></a> - <a href="break.html" title="cpp/language/break"><tt>break</tt></a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="goto.html" title="cpp/language/goto"><tt>goto</tt></a> - <a href="return.html" title="cpp/language/return"><tt>return</tt></a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> <a href="functions.html" title="cpp/language/functions"> Functions</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="function.html" title="cpp/language/function"> Function declaration</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="lambda.html" title="cpp/language/lambda"> Lambda function expression</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="inline.html" title="cpp/language/inline"> <code>inline</code> specifier</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="except_spec.html" title="cpp/language/except spec"> Dynamic exception specifications</a> <span class="t-mark-rev t-until-cxx20">(until C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="noexcept_spec.html" title="cpp/language/noexcept spec"> <code>noexcept</code> specifier</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h1"><td colspan="5"> Exceptions</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="throw.html" title="cpp/language/throw"> <code>throw</code>-expression</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="try_catch.html" title="cpp/language/try catch"> <code>try</code>-<code>catch</code> block</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> Namespaces</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="namespace.html" title="cpp/language/namespace"> Namespace declaration</a>  </td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="namespace_alias.html" title="cpp/language/namespace alias"> Namespace aliases</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> Types</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="types.html" title="cpp/language/types"> Fundamental types</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="enum_class.html" title="cpp/language/enum"> Enumeration types</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="function.html" title="cpp/language/function"> Function types</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="class.html" title="cpp/language/class"> Class/struct types</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="union.html" title="cpp/language/union"> Union types</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Specifiers</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="decltype.html" title="cpp/language/decltype"><tt>decltype</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="auto.html" title="cpp/language/auto"><tt>auto</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="alignas.html" title="cpp/language/alignas"><tt>alignas</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="cv.html" title="cpp/language/cv"> <code>const</code>/<code>volatile</code></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="constexpr.html" title="cpp/language/constexpr"><tt>constexpr</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="storage_duration.html" title="cpp/language/storage duration"> Storage duration specifiers</a></td></tr>
<tr class="t-nv-h2"><td colspan="5"> <a href="initialization.html" title="cpp/language/initialization"> Initialization</a></td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="default_initialization.html" title="cpp/language/default initialization"> Default initialization</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="value_initialization.html" title="cpp/language/value initialization"> Value initialization</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="zero_initialization.html" title="cpp/language/zero initialization"> Zero initialization</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="copy_initialization.html" title="cpp/language/copy initialization"> Copy initialization</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="direct_initialization.html" title="cpp/language/direct initialization"> Direct initialization</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="aggregate_initialization.html" title="cpp/language/aggregate initialization"> Aggregate initialization</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="list_initialization.html" title="cpp/language/list initialization"> List initialization</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="constant_initialization.html" title="cpp/language/constant initialization"> Constant initialization</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="reference_initialization.html" title="cpp/language/reference initialization"> Reference initialization</a></td></tr>
</table></div></td></tr>
</table></div>
</div>
<div style="display:inline-block">
<div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv-h1"><td colspan="5"> <a href="expressions.html" title="cpp/language/expressions"> Expressions</a></td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="value_category.html" title="cpp/language/value category"> Value categories</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="eval_order.html" title="cpp/language/eval order"> Order of evaluation</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="operators.html" title="cpp/language/operators"> Operators</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_precedence.html" title="cpp/language/operator precedence"> Operator precedence</a></td></tr>
</table></div></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_alternative.html" title="cpp/language/operator alternative"> Alternative representations</a></td></tr>
<tr class="t-nv-h2"><td colspan="5"> <a href="expressions.html#Literals" title="cpp/language/expressions"> Literals</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="bool_literal.html" title="cpp/language/bool literal"> Boolean</a> - <a href="integer_literal.html" title="cpp/language/integer literal"> Integer</a> - <a href="floating_literal.html" title="cpp/language/floating literal"> Floating-point</a></td></tr>   
<tr class="t-nv"><td colspan="5"> <a href="character_literal.html" title="cpp/language/character literal"> Character</a> - <a href="string_literal.html" title="cpp/language/string literal"> String</a> - <a href="nullptr.html" title="cpp/language/nullptr"><tt>nullptr</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr> 
<tr class="t-nv"><td colspan="5"> <a href="user_literal.html" title="cpp/language/user literal"> User-defined</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h1"><td colspan="5"> Utilities</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="attributes.html" title="cpp/language/attributes"> Attributes</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Types</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="typedef.html" title="cpp/language/typedef"> <code>typedef</code> declaration</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="type_alias.html" title="cpp/language/type alias"> Type alias declaration</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Casts</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="implicit_cast.html" title="cpp/language/implicit conversion"> Implicit conversions</a> - <a href="explicit_cast.html" title="cpp/language/explicit cast"> Explicit conversions</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="static_cast.html" title="cpp/language/static cast"><tt>static_cast</tt></a> - <a href="dynamic_cast.html" title="cpp/language/dynamic cast"><tt>dynamic_cast</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="const_cast.html" title="cpp/language/const cast"><tt>const_cast</tt></a> - <a href="reinterpret_cast.html" title="cpp/language/reinterpret cast"><tt>reinterpret_cast</tt></a></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Memory allocation</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="new.html" title="cpp/language/new"> <code>new</code> expression</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="delete.html" title="cpp/language/delete"> <code>delete</code> expression</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> <a href="classes.html" title="cpp/language/classes"> Classes</a></td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="class.html" title="cpp/language/class"> Class declaration</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="initializer_list.html" title="cpp/language/constructor"> Constructors</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="this.html" title="cpp/language/this"> <code>this</code> pointer</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="access.html" title="cpp/language/access"> Access specifiers</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="friend.html" title="cpp/language/friend"> <code>friend</code> specifier</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Class-specific function properties</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="virtual.html" title="cpp/language/virtual"> Virtual function</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="override.html" title="cpp/language/override"> <code>override</code> specifier</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="final.html" title="cpp/language/final"> <code>final</code> specifier</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="explicit.html" title="cpp/language/explicit"><tt>explicit</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="static.html" title="cpp/language/static"><tt>static</tt></a> </td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Special member functions</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="default_constructor.html" title="cpp/language/default constructor"> Default constructor</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="copy_constructor.html" title="cpp/language/copy constructor"> Copy constructor</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="move_constructor.html" title="cpp/language/move constructor"> Move constructor</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="as_operator.html" title="cpp/language/as operator" class="mw-redirect"> Copy assignment</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="move_operator.html" title="cpp/language/move operator" class="mw-redirect"> Move assignment</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="destructor.html" title="cpp/language/destructor"> Destructor</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"><a href="templates.html" title="cpp/language/templates"> Templates</a> </td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="class_template.html" title="cpp/language/class template"> Class template </a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="function_template.html" title="cpp/language/function template"> Function template </a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="template_specialization.html" title="cpp/language/template specialization"> Template specialization</a></td></tr>   
<tr class="t-nv"><td colspan="5"> <strong class="selflink"> Parameter packs</strong> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> Miscellaneous </td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="asm.html" title="cpp/language/asm"> Inline assembly</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="history.html" title="cpp/language/history"> History of C++</a></td></tr>
</table></div></td></tr>
</table></div>
</div><div></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="templates.html" title="cpp/language/templates"> Templates</a><div class="t-navbar-menu"><div><div style="display:inline-block">
<div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="template_parameters.html" title="cpp/language/template parameters"> Parameters and arguments</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="class_template.html" title="cpp/language/class template"> Class templates</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="function_template.html" title="cpp/language/function template"> Function templates</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="member_template.html" title="cpp/language/member template"> Class member templates</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="variable_template.html" title="cpp/language/variable template"> Variable templates</a> <span class="t-mark-rev t-since-cxx14">(C++14)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="template_argument_deduction.html" title="cpp/language/template argument deduction"> Template argument deduction</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="deduction_guide.html" title="cpp/language/class template argument deduction"> Class template argument deduction</a> <span class="t-mark-rev t-since-cxx17">(C++17)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="template_specialization.html" title="cpp/language/template specialization"> Explicit (full) specialization</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="partial_specialization.html" title="cpp/language/partial specialization"> Partial specialization</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="dependent_name.html" title="cpp/language/dependent name"> Dependent names</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <strong class="selflink"> Parameter packs</strong> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5">   <a href="sizeof....html" title="cpp/language/sizeof..."> <code>sizeof...</code></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5">   <a href="fold.html" title="cpp/language/fold"> Fold-expressions</a> <span class="t-mark-rev t-since-cxx17">(C++17)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="sfinae.html" title="cpp/language/sfinae"> SFINAE</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="constraints.html" title="cpp/language/constraints"> Constraints and concepts</a> <span class="t-mark-rev t-since-cxx20">(C++20)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="requires.html" title="cpp/language/requires"> Requires expression</a> <span class="t-mark-rev t-since-cxx20">(C++20)</span> </td></tr>
</table></div>
</div><div></div></div></div></div><div class="t-navbar-sep"> </div></div>
<p>A template parameter pack is a template parameter that accepts zero or more template arguments (non-types, types, or templates). A function parameter pack is a function parameter that accepts zero or more function arguments.
</p><p>A template with at least one parameter pack is called a <i>variadic template</i>.
</p>
<h3><span class="mw-headline" id="Syntax">Syntax</span></h3>
<p>Template parameter pack (appears in <a href="type_alias.html" title="cpp/language/type alias">alias template</a>, 
<a href="class_template.html" title="cpp/language/class template">class template</a><span class="t-rev-inl t-since-cxx14"><span>, <a href="variable_template.html" title="cpp/language/variable template">variable template</a></span> <span><span class="t-mark-rev t-since-cxx14">(since C++14)</span></span></span> and <a href="function_template.html" title="cpp/language/function template">function template</a> parameter lists)
</p>
<table class="t-sdsc-begin">

<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">type</span> <code><b>...</b></code> <span class="t-spar">pack-name</span><span class="t-mark">(optional)</span>
</td>
<td> (1)
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <code><b>typename</b></code><code><b>|</b></code><code><b>class</b></code> <code><b>...</b></code> <span class="t-spar">pack-name</span><span class="t-mark">(optional)</span>
</td>
<td> (2)
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">type-constraint</span> <code><b>...</b></code> <span class="t-spar">pack-name</span><span class="t-mark">(optional)</span>
</td>
<td> (3)
</td>
<td> <span class="t-mark-rev t-since-cxx20">(since C++20)</span>
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <code><b>template</b></code> <code><b>&lt;</b></code> <span class="t-spar">parameter-list</span> <code><b>&gt;</b></code> <code><b>class</b></code> <code><b>...</b></code> <span class="t-spar">pack-name</span><span class="t-mark">(optional)</span>
</td>
<td> (4)
</td>
<td> <span class="t-mark-rev t-until-cxx17">(until C++17)</span>
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <code><b>template</b></code> <code><b>&lt;</b></code> <span class="t-spar">parameter-list</span> <code><b>&gt;</b></code> <code><b>typename</b></code><code><b>|</b></code><code><b>class</b></code> <code><b>...</b></code> <span class="t-spar">pack-name</span><span class="t-mark">(optional)</span>
</td>
<td> (4)
</td>
<td> <span class="t-mark-rev t-since-cxx17">(since C++17)</span>
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<p>Function parameter pack (a form of <a href="declarations.html" title="cpp/language/declarations">declarator</a>, appears in a function parameter list of a variadic function template)
</p>
<table class="t-sdsc-begin">

<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">pack-name</span> <code><b>...</b></code> <span class="t-spar">pack-param-name</span><span class="t-mark">(optional)</span>
</td>
<td> (5)
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<p>Parameter pack expansion (appears in a body of a variadic template)
</p>
<table class="t-sdsc-begin">

<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">pattern</span> <code><b>...</b></code>
</td>
<td> (6)
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<div class="t-li1"><span class="t-li">1)</span> A non-type template parameter pack with an optional name</div>
<div class="t-li1"><span class="t-li">2)</span> A type template parameter pack with an optional name</div>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx20"><td>
<div class="t-li1"><span class="t-li">3)</span> A <a href="constraints.html" title="cpp/language/constraints">constrained</a> type template parameter pack with an optional name
</div></td>
<td><span class="t-mark-rev t-since-cxx20">(since C++20)</span></td></tr>
</table>
<div class="t-li1"><span class="t-li">4)</span> A template template parameter pack with an optional name</div>
<div class="t-li1"><span class="t-li">5)</span> A function parameter pack with an optional name</div>
<div class="t-li1"><span class="t-li">6)</span> Parameter pack expansion: expands to comma-separated list of zero or more <code>pattern</code>s. Pattern must include at least one parameter pack.</div>
<h3><span class="mw-headline" id="Explanation">Explanation</span></h3>
<p>A variadic class template can be instantiated with any number of template arguments:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Types</span><span class="sy1">&gt;</span>
<span class="kw1">struct</span> Tuple <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
 
Tuple<span class="sy1">&lt;&gt;</span> t0<span class="sy4">;</span>           <span class="co1">// Types contains no arguments</span>
Tuple<span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> t1<span class="sy4">;</span>        <span class="co1">// Types contains one argument: int</span>
Tuple<span class="sy1">&lt;</span><span class="kw4">int</span>, <span class="kw4">float</span><span class="sy1">&gt;</span> t2<span class="sy4">;</span> <span class="co1">// Types contains two arguments: int and float</span>
Tuple<span class="sy1">&lt;</span><span class="nu0">0</span><span class="sy1">&gt;</span> t3<span class="sy4">;</span>          <span class="co1">// error: 0 is not a type</span></pre></div></div>
<p>A variadic function template can be called with any number of function arguments (the template arguments are deduced through <a href="template_argument_deduction.html" title="cpp/language/template argument deduction">template argument deduction</a>):
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Types</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> f<span class="br0">(</span>Types... <span class="me1">args</span><span class="br0">)</span><span class="sy4">;</span>
 
f<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>       <span class="co1">// OK: args contains no arguments</span>
f<span class="br0">(</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>      <span class="co1">// OK: args contains one argument: int</span>
f<span class="br0">(</span><span class="nu0">2</span>, <span class="nu16">1.0</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// OK: args contains two arguments: int and double</span></pre></div></div>
<p>In a primary class template, the template parameter pack must be the final parameter in the template parameter list. In a function template, the template parameter pack may appear earlier in the list provided that all following parameters can be deduced from the function arguments, or have default arguments:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> U, <span class="kw1">typename</span>... <span class="me1">Ts</span><span class="sy1">&gt;</span>    <span class="co1">// OK: can deduce U</span>
<span class="kw1">struct</span> valid<span class="sy4">;</span>
<span class="co1">// template&lt;typename... Ts, typename U&gt; // Error: Ts... not at the end</span>
<span class="co1">// struct Invalid;</span>
 
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span>... <span class="me1">Ts</span>, <span class="kw1">typename</span> U, <span class="kw1">typename</span><span class="sy1">=</span><span class="kw4">void</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> valid<span class="br0">(</span>U, Ts...<span class="br0">)</span><span class="sy4">;</span>    <span class="co1">// OK: can deduce U</span>
<span class="co1">// void valid(Ts..., U); // Can't be used: Ts... is a non-deduced context in this position</span>
 
valid<span class="br0">(</span><span class="nu16">1.0</span>, <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span><span class="br0">)</span><span class="sy4">;</span>     <span class="co1">// OK: deduces U as double, Ts as {int, int, int}</span></pre></div></div>
<p>If every valid specialization of a variadic template requires an empty template parameter pack, the program is ill-formed, no diagnostic required.
</p>
<h3><span class="mw-headline" id="Pack_expansion">Pack expansion</span></h3>
<p>A pattern followed by an ellipsis, in which the name of at least one parameter pack appears at least once, is <i>expanded</i> into zero or more comma-separated instantiations of the pattern, where the name of the parameter pack is replaced by each of the elements from the pack, in order.
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Us</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> f<span class="br0">(</span>Us... <span class="me1">pargs</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
 
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Ts</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> g<span class="br0">(</span>Ts... <span class="me1">args</span><span class="br0">)</span>
<span class="br0">{</span>
    f<span class="br0">(</span><span class="sy3">&amp;</span>args...<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// “&amp;args...” is a pack expansion</span>
                 <span class="co1">// “&amp;args” is its pattern</span>
<span class="br0">}</span>
 
g<span class="br0">(</span><span class="nu0">1</span>, <span class="nu16">0.2</span>, <span class="st0">"a"</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// Ts... args expand to int E1, double E2, const char* E3</span>
                <span class="co1">// &amp;args... expands to &amp;E1, &amp;E2, &amp;E3</span>
                <span class="co1">// Us... pargs expand to int* E1, double* E2, const char** E3</span></pre></div></div>
<p>If the names of two parameter packs appear in the same pattern, they are expanded simultaneously, and they must have the same length:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span>...<span class="sy1">&gt;</span>
<span class="kw1">struct</span> Tuple <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T1, <span class="kw1">typename</span> T2<span class="sy1">&gt;</span>
<span class="kw1">struct</span> Pair <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Args1</span><span class="sy1">&gt;</span>
<span class="kw1">struct</span> zip
<span class="br0">{</span>
    <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Args2</span><span class="sy1">&gt;</span>
    <span class="kw1">struct</span> with
    <span class="br0">{</span>
        <span class="kw1">typedef</span> Tuple<span class="sy1">&lt;</span>Pair<span class="sy1">&lt;</span>Args1, Args2<span class="sy1">&gt;</span>...<span class="sy1">&gt;</span> type<span class="sy4">;</span>
        <span class="co1">// Pair&lt;Args1, Args2&gt;... is the pack expansion</span>
        <span class="co1">// Pair&lt;Args1, Args2&gt; is the pattern</span>
    <span class="br0">}</span><span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw1">typedef</span> zip<span class="sy1">&lt;</span><span class="kw4">short</span>, <span class="kw4">int</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">with</span><span class="sy1">&lt;</span><span class="kw4">unsigned</span> <span class="kw4">short</span>, <span class="kw4">unsigned</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">type</span> T1<span class="sy4">;</span>
<span class="co1">// Pair&lt;Args1, Args2&gt;... expands to</span>
<span class="co1">// Pair&lt;short, unsigned short&gt;, Pair&lt;int, unsigned int&gt; </span>
<span class="co1">// T1 is Tuple&lt;Pair&lt;short, unsigned short&gt;, Pair&lt;int, unsigned&gt;&gt;</span>
 
<span class="co1">// typedef zip&lt;short&gt;::with&lt;unsigned short, unsigned&gt;::type T2;</span>
<span class="co1">// error: pack expansion contains parameter packs of different lengths</span></pre></div></div>
<p>If a pack expansion is nested within another pack expansion, the parameter packs that appear inside the innermost pack expansion are expanded by it, and there must be another pack mentioned in the enclosing pack expansion, but not in the innermost one:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Args</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> g<span class="br0">(</span>Args... <span class="me1">args</span><span class="br0">)</span>
<span class="br0">{</span>
    f<span class="br0">(</span><span class="kw1">const_cast</span><span class="sy1">&lt;</span><span class="kw4">const</span> Args<span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="sy4">;</span> 
    <span class="co1">// const_cast&lt;const Args*&gt;(&amp;args) is the pattern, it expands two packs</span>
    <span class="co1">// (Args and args) simultaneously</span>
 
    f<span class="br0">(</span>h<span class="br0">(</span>args...<span class="br0">)</span> <span class="sy2">+</span> args...<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// Nested pack expansion:</span>
    <span class="co1">// inner pack expansion is "args...", it is expanded first</span>
    <span class="co1">// outer pack expansion is h(E1, E2, E3) + args..., it is expanded</span>
    <span class="co1">// second (as h(E1, E2, E3) + E1, h(E1, E2, E3) + E2, h(E1, E2, E3) + E3)</span>
<span class="br0">}</span></pre></div></div>
<h3><span class="mw-headline" id="Expansion_loci">Expansion loci</span></h3>
<p>Depending on where the expansion takes place, the resulting comma-separated list is a different kind of list: function parameter list, member initializer list, attribute list, etc. The following is the list of all allowed contexts:
</p>
<h4><span class="mw-headline" id="Function_argument_lists">Function argument lists</span></h4>
<p>A pack expansion may appear inside the parentheses of a function call operator, in which case the largest expression or braced-init-list to the left of the ellipsis is the pattern that is expanded:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1">f<span class="br0">(</span><span class="sy3">&amp;</span>args...<span class="br0">)</span><span class="sy4">;</span>             <span class="co1">// expands to f(&amp;E1, &amp;E2, &amp;E3)</span>
f<span class="br0">(</span>n, <span class="sy2">++</span>args...<span class="br0">)</span><span class="sy4">;</span>         <span class="co1">// expands to f(n, ++E1, ++E2, ++E3);</span>
f<span class="br0">(</span><span class="sy2">++</span>args..., n<span class="br0">)</span><span class="sy4">;</span>         <span class="co1">// expands to f(++E1, ++E2, ++E3, n);</span>
 
f<span class="br0">(</span><span class="kw1">const_cast</span><span class="sy1">&lt;</span><span class="kw4">const</span> Args<span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>args<span class="br0">)</span>...<span class="br0">)</span><span class="sy4">;</span>
<span class="co1">// f(const_cast&lt;const E1*&gt;(&amp;X1), const_cast&lt;const E2*&gt;(&amp;X2), const_cast&lt;const E3*&gt;(&amp;X3))</span>
 
f<span class="br0">(</span>h<span class="br0">(</span>args...<span class="br0">)</span> <span class="sy2">+</span> args...<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// expands to </span>
<span class="co1">// f(h(E1, E2, E3) + E1, h(E1, E2, E3) + E2, h(E1, E2, E3) + E3)</span></pre></div></div>
<p>Formally, the <i>expression-list</i> in a function call expression is classified as <i>initializer-list</i>, and the pattern is the <i>initializer-clause</i>, which is either an <i>assignment-expression</i> or a <i>braced-init-list</i>.
</p>
<h4><span class="mw-headline" id="Parenthesized_initializers">Parenthesized initializers</span></h4>
<p>A pack expansion may appear inside the parentheses of a <a href="direct_initialization.html" title="cpp/language/direct initialization">direct initializer</a>, a <a href="explicit_cast.html" title="cpp/language/explicit cast">function-style cast</a>, and other contexts (<a href="initializer_list.html" title="cpp/language/initializer list" class="mw-redirect">member initializer</a>, <a href="new.html" title="cpp/language/new">new-expression</a>, etc.) in which case the rules are identical to the rules for a function call expression above:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1">Class c1<span class="br0">(</span><span class="sy3">&amp;</span>args...<span class="br0">)</span><span class="sy4">;</span>             <span class="co1">// calls Class::Class(&amp;E1, &amp;E2, &amp;E3)</span>
Class c2 <span class="sy1">=</span> Class<span class="br0">(</span>n, <span class="sy2">++</span>args...<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// calls Class::Class(n, ++E1, ++E2, ++E3);</span>
 
<span class="sy4">::</span><span class="me2">new</span><span class="br0">(</span><span class="br0">(</span><span class="kw4">void</span> <span class="sy2">*</span><span class="br0">)</span>p<span class="br0">)</span> U<span class="br0">(</span><a href="../utility/forward.html"><span class="kw1120">std::<span class="me2">forward</span></span></a><span class="sy1">&lt;</span>Args<span class="sy1">&gt;</span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span> <span class="co1">// std::allocator::allocate</span></pre></div></div>
<h4><span class="mw-headline" id="Brace-enclosed_initializers">Brace-enclosed initializers</span></h4>
<p>In a <i>braced-init-list</i> (brace-enclosed list of initializers and other <i>braced-init-list</i>s, used in <a href="list_initialization.html" title="cpp/language/list initialization">list-initialization</a> and some other contexts), a pack expansion may appear as well:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span>... <span class="me1">Ts</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> func<span class="br0">(</span>Ts... <span class="me1">args</span><span class="br0">)</span>
<span class="br0">{</span>
    <span class="kw4">const</span> <span class="kw4">int</span> size <span class="sy1">=</span> sizeof...<span class="br0">(</span>args<span class="br0">)</span> <span class="sy2">+</span> <span class="nu0">2</span><span class="sy4">;</span>
    <span class="kw4">int</span> res<span class="br0">[</span>size<span class="br0">]</span> <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">1</span>, args..., <span class="nu0">2</span><span class="br0">}</span><span class="sy4">;</span>
 
    <span class="co1">// since initializer lists guarantee sequencing, this can be used to</span>
    <span class="co1">// call a function on each element of a pack, in order:</span>
    <span class="kw4">int</span> dummy<span class="br0">[</span>sizeof...<span class="br0">(</span>Ts<span class="br0">)</span><span class="br0">]</span> <span class="sy1">=</span> <span class="br0">{</span><span class="br0">(</span><a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> args, <span class="nu0">0</span><span class="br0">)</span>...<span class="br0">}</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<h4><span class="mw-headline" id="Template_argument_lists">Template argument lists</span></h4>
<p>Pack expansions can be used anywhere in a template argument list, provided the template has the parameters to match the expansion:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> A, <span class="kw1">class</span> B, <span class="kw1">class</span>... <span class="me1">C</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> func<span class="br0">(</span>A arg1, B arg2, C... <span class="me1">arg3</span><span class="br0">)</span>
<span class="br0">{</span>
    container<span class="sy1">&lt;</span>A, B, C...<span class="sy1">&gt;</span> t1<span class="sy4">;</span> <span class="co1">// expands to container&lt;A, B, E1, E2, E3&gt; </span>
    container<span class="sy1">&lt;</span>C..., A, B<span class="sy1">&gt;</span> t2<span class="sy4">;</span> <span class="co1">// expands to container&lt;E1, E2, E3, A, B&gt; </span>
    container<span class="sy1">&lt;</span>A, C..., B<span class="sy1">&gt;</span> t3<span class="sy4">;</span> <span class="co1">// expands to container&lt;A, E1, E2, E3, B&gt; </span>
<span class="br0">}</span></pre></div></div>
<h4><span class="mw-headline" id="Function_parameter_list">Function parameter list</span></h4>
<p>In a function parameter list, if an ellipsis appears in a parameter declaration (whether it names a function parameter pack (as in, <span class="t-spar">Args</span><code><b>...</b></code> <span class="t-spar">args</span>) or not) the parameter declaration is the pattern:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span>... <span class="me1">Ts</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> f<span class="br0">(</span>Ts...<span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
 
f<span class="br0">(</span><span class="st0">'a'</span>, <span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// Ts... expands to void f(char, int)</span>
f<span class="br0">(</span><span class="nu16">0.1</span><span class="br0">)</span><span class="sy4">;</span>    <span class="co1">// Ts... expands to void f(double)</span>
 
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span>... <span class="me1">Ts</span>, <span class="kw4">int</span>... <span class="me1">N</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> g<span class="br0">(</span>Ts <span class="br0">(</span><span class="sy3">&amp;</span>...<span class="me1">arr</span><span class="br0">)</span><span class="br0">[</span>N<span class="br0">]</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
 
<span class="kw4">int</span> n<span class="br0">[</span><span class="nu0">1</span><span class="br0">]</span><span class="sy4">;</span>
g<span class="sy1">&lt;</span><span class="kw4">const</span> <span class="kw4">char</span>, <span class="kw4">int</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="st0">"a"</span>, n<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// Ts (&amp;...arr)[N] expands to </span>
                            <span class="co1">// const char (&amp;)[2], int(&amp;)[1]</span></pre></div></div>
<p>Note: In the pattern <code>Ts (&amp;...arr)[N]</code>, the ellipsis is the innermost element, not the last element as in all other pack expansions.
</p><p>Note: <code>Ts (&amp;...)[N]</code> is not allowed because the C++11 grammar requires the parenthesized ellipsis to have a name: <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/1488.html">CWG issue 1488</a>.
</p>
<h4><span class="mw-headline" id="Template_parameter_list">Template parameter list</span></h4>
<p>Pack expansion may appear in a template parameter list:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span>... <span class="me1">T</span><span class="sy1">&gt;</span>
<span class="kw1">struct</span> value_holder
<span class="br0">{</span>
    <span class="kw1">template</span><span class="sy1">&lt;</span>T... <span class="me1">Values</span><span class="sy1">&gt;</span> <span class="co1">// expands to a non-type template parameter </span>
    <span class="kw1">struct</span> apply <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>      <span class="co1">// list, such as &lt;int, char, int(&amp;)[5]&gt;</span>
<span class="br0">}</span><span class="sy4">;</span></pre></div></div>
<h4><span class="mw-headline" id="Base_specifiers_and_member_initializer_lists">Base specifiers and member initializer lists</span></h4>
<p>A pack expansion may designate the list of base classes in a <a href="class.html" title="cpp/language/class">class declaration</a>. Typically, this also means that the constructor needs to use a pack expansion in the <a href="initializer_list.html" title="cpp/language/initializer list" class="mw-redirect">member initializer list</a> to call the constructors of these bases:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Mixins</span><span class="sy1">&gt;</span>
<span class="kw1">class</span> X <span class="sy4">:</span> <span class="kw1">public</span> Mixins...
<span class="br0">{</span>
<span class="kw1">public</span><span class="sy4">:</span>
    X<span class="br0">(</span><span class="kw4">const</span> Mixins<span class="sy3">&amp;</span>... <span class="me1">mixins</span><span class="br0">)</span> <span class="sy4">:</span> Mixins<span class="br0">(</span>mixins<span class="br0">)</span>... <span class="br0">{</span><span class="br0">}</span>
<span class="br0">}</span><span class="sy4">;</span></pre></div></div>
<h4><span class="mw-headline" id="Lambda_captures">Lambda captures</span></h4>
<p>Pack expansion may appear in the capture clause of a <a href="lambda.html" title="cpp/language/lambda">lambda</a> expression:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Args</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> f<span class="br0">(</span>Args... <span class="me1">args</span><span class="br0">)</span>
<span class="br0">{</span>
    <span class="kw4">auto</span> lm <span class="sy1">=</span> <span class="br0">[</span><span class="sy3">&amp;</span>, args...<span class="br0">]</span> <span class="br0">{</span> <span class="kw1">return</span> g<span class="br0">(</span>args...<span class="br0">)</span><span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span>
    lm<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<h4><span class="mw-headline" id="The_sizeof..._operator">The sizeof... operator</span></h4>
<p>The <a href="sizeof....html" title="cpp/language/sizeof..."><code>sizeof...</code></a> operator is classified as a pack expansion as well:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">Types</span><span class="sy1">&gt;</span>
<span class="kw1">struct</span> count
<span class="br0">{</span>
    <span class="kw4">static</span> <span class="kw4">const</span> <a href="../types/size_t.html"><span class="kw106">std::<span class="me2">size_t</span></span></a> value <span class="sy1">=</span> sizeof...<span class="br0">(</span>Types<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span></pre></div></div>
 <table class="t-rev-begin">
<tr class="t-rev t-until-cxx17"><td>
<h4> <span class="mw-headline" id="Dynamic_exception_specifications">Dynamic exception specifications</span></h4>
<p>The list of exceptions in a <a href="except_spec.html" title="cpp/language/except spec">dynamic exception specification</a> may also be a pack expansion:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span>... <span class="me1">X</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> func<span class="br0">(</span><span class="kw4">int</span> arg<span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span>X...<span class="br0">)</span>
<span class="br0">{</span>
    <span class="co1">// ... throw different Xs in different situations</span>
<span class="br0">}</span></pre></div></div>
</td>
<td><span class="t-mark-rev t-until-cxx17">(until C++17)</span></td></tr>
</table>
<h4><span class="mw-headline" id="Alignment_specifier">Alignment specifier</span></h4>
<p>Pack expansions are allowed in both the lists of types and the lists of expressions used by the keyword <a href="alignas.html" title="cpp/language/alignas"><code>alignas</code></a>.
</p>
<h4><span class="mw-headline" id="Attribute_list">Attribute list</span></h4>
<p>Pack expansions are allowed in the lists of <a href="attributes.html" title="cpp/language/attributes">attributes</a>, as in <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">[</span><span class="br0">[</span>attributes...<span class="br0">]</span><span class="br0">]</span></span></span>. For example: <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> <span class="br0">[</span><span class="br0">[</span>attributes...<span class="br0">]</span><span class="br0">]</span> function<span class="br0">(</span><span class="br0">)</span></span></span>
</p>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx17"><td>
<h4> <span class="mw-headline" id="Fold-expressions">Fold-expressions</span></h4>
<p>In <a href="fold.html" title="cpp/language/fold">fold-expressions</a>, the pattern is the entire subexpression that does not contain an unexpanded parameter pack.
</p>
<h4> <span class="mw-headline" id="Using-declarations">Using-declarations</span></h4>
<p>In <a href="using_declaration.html" title="cpp/language/using declaration">using declaration</a>, ellipsis may appear in the list of declarators, this is useful when deriving from a parameter pack:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span>... <span class="me1">bases</span><span class="sy1">&gt;</span>
<span class="kw1">struct</span> X <span class="sy4">:</span> bases...
<span class="br0">{</span>
    <span class="kw1">using</span> bases<span class="sy4">::</span><span class="me2">g</span>...<span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span>
X<span class="sy1">&lt;</span>B, D<span class="sy1">&gt;</span> x<span class="sy4">;</span> <span class="co1">// OK: B::g and D::g introduced</span></pre></div></div>
</td>
<td><span class="t-mark-rev t-since-cxx17">(since C++17)</span></td></tr>
</table>
<h3><span class="mw-headline" id="Notes">Notes</span></h3>
<table class="metadata plainlinks ambox mbox-small-left ambox-notice" style=""><tr><td class="mbox-empty-cell"></td><td class="mbox-text" style="">This section is incomplete<br>Reason: a few words about partial specializations and other ways to access individual elements? Mention recursion vs logarithmic vs shortcuts such as fold expressions </td></tr></table>
<h3><span class="mw-headline" id="Example">Example</span></h3>
<p>The below example defines a function similar to <span class="t-lc"><a href="../io/c/printf.html" title="cpp/io/c/fprintf">std::printf</a></span>, that replace each occurrence of the character <code>%</code> in the format string with a value.
</p><p>The first overload is called when only the format string is passed and there is no parameter expansion.
</p><p>The second overload contains a separate template parameter for the head of the arguments and a parameter pack, this allows the recursive call to pass only the tail of the parameters until it becomes empty.
</p><p><code><b>Targs</b></code> is the template parameter pack and <code><b>Fargs</b></code> is the function parameter pack.
</p>
<div class="t-example"><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
 
<span class="kw4">void</span> tprintf<span class="br0">(</span><span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> format<span class="br0">)</span> <span class="co1">// base function</span>
<span class="br0">{</span>
    <a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> format<span class="sy4">;</span>
<span class="br0">}</span>
 
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">typename</span> T, <span class="kw1">typename</span>... <span class="me1">Targs</span><span class="sy1">&gt;</span>
<span class="kw4">void</span> tprintf<span class="br0">(</span><span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> format, T value, Targs... <span class="me1">Fargs</span><span class="br0">)</span> <span class="co1">// recursive variadic function</span>
<span class="br0">{</span>
    <span class="kw1">for</span> <span class="br0">(</span><span class="sy4">;</span> <span class="sy2">*</span>format <span class="sy3">!</span><span class="sy1">=</span> <span class="st0">'<span class="es5">\0</span>'</span><span class="sy4">;</span> format<span class="sy2">++</span><span class="br0">)</span>
    <span class="br0">{</span>
        <span class="kw1">if</span> <span class="br0">(</span><span class="sy2">*</span>format <span class="sy1">==</span> <span class="st0">'%'</span><span class="br0">)</span>
        <span class="br0">{</span>
            <a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> value<span class="sy4">;</span>
            tprintf<span class="br0">(</span>format <span class="sy2">+</span> <span class="nu0">1</span>, Fargs...<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// recursive call</span>
            <span class="kw1">return</span><span class="sy4">;</span>
        <span class="br0">}</span>
        <a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="sy2">*</span>format<span class="sy4">;</span>
    <span class="br0">}</span>
<span class="br0">}</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    tprintf<span class="br0">(</span><span class="st0">"% world% %<span class="es1">\n</span>"</span>, <span class="st0">"Hello"</span>, <span class="st0">'!'</span>, <span class="nu0">123</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<p>Output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">Hello world! 123</pre></div></div> 
</div>
<h3><span class="mw-headline" id="Defect_reports">Defect reports</span></h3>
<p>The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
</p>
<table class="dsctable" style="font-size:0.8em">
<tr>
<th> DR
</th>
<th> Applied to
</th>
<th> Behavior as published
</th>
<th> Correct behavior
</th></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/1533.html">CWG 1533</a>
</td>
<td> C++11
</td>
<td> a pack expansion could occur in a member initializer for a member
</td>
<td> not allowed
</td></tr></table>
<h3><span class="mw-headline" id="See_also">See also</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc">
<td colspan="2"> <a href="function_template.html" title="cpp/language/function template">function template</a>
</td></tr>


<tr class="t-dsc">
<td colspan="2"> <a href="class_template.html" title="cpp/language/class template">class template</a>
</td></tr>


<tr class="t-dsc">
<td> <a href="sizeof....html" title="cpp/language/sizeof..."><code>sizeof...</code></a>
</td>
<td> Queries the number of elements in a parameter pack.
</td></tr>


<tr class="t-dsc">
<td colspan="2"> <a href="../utility/variadic.html" title="cpp/utility/variadic">C-style variadic functions</a>
</td></tr>


<tr class="t-dsc">
<td> <a href="../preprocessor/replace.html" title="cpp/preprocessor/replace">Preprocessor macros</a>
</td>
<td> Can be variadic as well
</td></tr>


<tr class="t-dsc">
<td colspan="2"> <a href="fold.html" title="cpp/language/fold">Fold expressions</a>
</td></tr>

</table>

<!-- 
NewPP limit report
Preprocessor visited node count: 4014/1000000
Preprocessor generated node count: 11734/1000000
Post‐expand include size: 140821/2097152 bytes
Template argument size: 25627/2097152 bytes
Highest expansion depth: 17/40
Expensive parser function count: 0/100
-->

<!-- Saved in parser cache with key mwiki1-mwiki_en_:pcache:idhash:9639-0!*!0!!en!*!* and timestamp 20220710180059 -->
</div>                    <!-- /bodycontent -->
                                        <!-- printfooter -->
                    <div class="printfooter">
                    Retrieved from "<a href="https://en.cppreference.com/mwiki/index.php?title=cpp/language/parameter_pack&amp;oldid=140905">https://en.cppreference.com/mwiki/index.php?title=cpp/language/parameter_pack&amp;oldid=140905</a>"                    </div>
                    <!-- /printfooter -->
                                                            <!-- catlinks -->
                    <!-- /catlinks -->
                                                            <div class="visualClear"></div>
                    <!-- debughtml -->
                                        <!-- /debughtml -->
                </div>
                <!-- /bodyContent -->
            </div>
        </div>
        <!-- /content -->
        <!-- footer -->
        <div id="cpp-footer-base" class="noprint">
            <div id="footer">
                        <div id="cpp-navigation">
            <h5>Navigation</h5>
            <ul><li><a href="https://en.cppreference.com/w/cpp/language/parameter_pack">Online version</a></li><li>Offline version retrieved 2022-07-30 14:05.</li></ul></div>
                        <ul id="footer-info">
                                    <li id="footer-info-lastmod"> This page was last modified on 10 July 2022, at 11:00.</li>
                                    <li id="footer-info-viewcount">This page has been accessed 1,432,263 times.</li>
                            </ul>
                    </div>
        </div>
        <!-- /footer -->
        <script>if(window.mw){
mw.loader.state({"site":"loading","user":"missing","user.groups":"ready"});
}</script>
<script src="../../../common/skin_scripts.js"></script>
<script>if(window.mw){
mw.loader.load(["mediawiki.action.view.postEdit","mediawiki.user","mediawiki.page.ready","mediawiki.searchSuggest","mediawiki.hidpi","ext.gadget.ColiruCompiler","ext.gadget.MathJax"], null, true);
}</script>
<script src="../../../common/site_scripts.js"></script>
<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-2828341-1']);
_gaq.push(['_setDomainName', 'cppreference.com']);
_gaq.push(['_trackPageview']);
</script><!-- Served in 0.040 secs. -->
	</body>
<!-- Cached 20220710180257 -->
</html>